Nonwoven thermally insulating elastically stretchable fabrics are taught in U.S. Pat. No. 4,551,378. Although these fabrics offer good insulating properties and comfort in wearing, the present invention makes possible even better insulating properties. Fabric as taught in U.S. Pat. No. 4,551,378 can be a component of fabric of the invention.
A different stretchable nonwoven thermal insulating fabric, which in one embodiment comprises a nonwoven web formed from thin fibrous layers laminated together, with the fibers comprising a polyester type copolymer containing butylene terephthalate, is taught in U.S. Pat. No. 4,438,172.
Another nonwoven thermal insulating fabric having stretch properties is commercially available under the trademark "Viwarm" from a Japanese manufacturer. The material is a spray-bonded, lightly needle-tacked nonwoven web of a blend of one- and three-denier single-component polyester fibers, the three-denier fiber having sufficient crimp to provide stretch properties. The product has a high "power stretch" (i.e., it requires a large force to stretch the fabric), and it does not have the combination of thermal insulating properties and low density offered in the present invention.
A different item of background prior art, relevant because it teaches blends of fibers useful in some embodiments of the present invention, is U.S. Pat. No. 4,118,531. This patent teaches blends of melt-blown microfibers and crimped staple textile fibers, which form lofty, high-insulating-value fabric or sheet material.